THIS week’s attack was the worst in London for 12 years and has caused shock and horror, especially for the way in which a vehicle was so easily and violently used to killed innocent pedestrians. We will know in the coming days the extent to which this was an individual attack or whether it involved others and, if the latter, why there was apparently no warning.

The immediate reaction is to think of the families and friends of the victims and that is right and proper, but in due course we have to look at why there is still this threat. Britain has now been involved in the “war on terror” for over 15 years, yet the sense of fear and concern over the risk of attacks is as high as it has even been. Why is this so?

One core issue makes for difficult reading and it concerns the “disconnect” in Britain between the terrible event this week and the continuing war in Iraq. It is a disconnect that was very visible when the Blair government denied any link between the 7/7 atrocities and the war in Iraq which was then at its height.

Now, nearly 12 years later, the war goes on with a similar linkage largely ignored. There is simply no appreciation that Britain is an integral part of a major air war that began over thirty months ago, in August 2014. It may take the form of a sustained air-assault using strike aircraft and armed drones rather than troops on the ground, but its intensity is simply unrecognised in most of the mainstream media.

People will naturally react with horror to the attack, asking – why us? Politicians and analysts will find it very difficult even to try and explain the connection between what is happening “there” and “here”.

The straightforward, yet uncomfortable answer, is that Britain is at war. It may be a war that gets little attention, there may be virtually no parliamentary debate on its conduct, but it is a war nonetheless. So what else should be expected other than it sometimes hits us at home?

There are several factors which underpin the situation.

The post-9/11 western-led conflicts in Iraq, Afghanistan, and Libya have left three countries as failed or failing states, killed several hundred thousand people and displaced millions. This causes persistent anger and bitterness right across the Middle East and beyond. While the Syrian civil war started as the repression of dissent by an insecure and harsh regime, it has evolved into a much more complex conflict which regional rulers and the wider international community have failed to address. This adds to the animosity.

The situation in Iraq is particularly grievous given that it was the United States and its coalition partners that started the conflict and also gave rise directly to the evolution of Islamic State (IS). Reliable estimates put the direct civilian death-toll there since 2003 at more than 169,000. After a relative decline over 2009-13, an upsurge in the past three years has seen another 53,000 lose their lives through violence.

And then there is the air war against IS. Since that started in 2014, the Pentagon calculates that over 30,000 targets have been attacked with more than 60,000 missiles and bombs, and 50,000 IS supporters have been killed. There is also abundant evidence from independent sources that western forces have, at the same time, directly killed many civilians, probably more than 3,000.

IS and other groups have no air-defence capabilities yet are determined to continue the war, seeing themselves as guardians of Islam under attack by the “crusader” forces of the west. At a time of retreat they will be even more determined than ever to take the war to the enemy, whether by the sustained encouragement and even facilitation of individual attacks such as Berlin, Istanbul, Nice and possibly now London, or more organised attacks such as in Paris and Brussels.

* Demonstrating to the wider world, especially across the Middle East, that they remain a force to be reckoned with;

* Inciting as much anti-Muslim bigotry and hatred as possible in the target countries.

How should we best respond to what has happened in London? Two issues are relevant.

First, the aim of IS and others will be to incite hatred. Any tendency to encourage that is doing the work of IS. This can and should be said repeatedly. It is crucial at this time to work as hard as we can to hold communities together – “hope not hate” is the way forward and anything else does IS’s work.

Second, the fact that Britain is still at war after 15 years surely means that some serious rethinking is required about foreign policy. In the immediate aftermath of the shock of what happened in London, that may be too much to ask, but in the coming months we really do have to do just that.

Paul Rogers is Professor of Peace Studies at Bradford University and author of Irregular War: ISIS and the New Threats from the Margins (I B Tauris).

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